An electromagnetic induction-type displacement sensor (position detection device) has been provided which includes two detection circuits (detectors) so that even when a fault occurs on one of the detectors, displacement of an object is detectable by the other of the detectors. Such a position detection device has been disclosed in, for example, Document 1 (JP 2005-265463 A). The position detection device includes two detectors each including a coil drive unit, two drive coils (excitation coils) each connected to the coil drive unit, and two detection coils each connected to the detector. The position detection device further includes an electromagnetic coupling member displaceable relatively to the excitation coils and the detection coils. The coil drive units include oscillation circuits each connected to a corresponding one of the excitation coils and timers each configured to output an oscillation inhibiting signal to the oscillation circuit of the other of the coil drive units.
In this position detection device, while one of the coil drive units drives the excitation coil, drive of the other of the excitation coils is interrupted by the oscillation inhibiting signal of the timer of the one coil drive unit, thereby allowing the two detectors to detect the displacement of the electromagnetic coupling member in a time sharing manner.
However, the conventional example described above does not consider a circumstance in which drive periods of the excitation coils overlap each other on activation of the detectors. Therefore, in the conventional example described above, when the drive periods of the excitation coils overlap each other on activation of the detectors, for example, detection processes by the detectors may be simultaneously performed, which may lead to mutual magnetic interference.